Ultra high pressure-high temperature apparatus



Feb. 3, 1970 TTTTTTTTTT Tom 3,492,695

ed June 14, 1967 Feb. 3, 1970 'VI'ATSUO KURATOMI 3,492,695

ULTRA HIGH PRESSURE-HIGH TEMPERATURE APPARATUS Filed June 14, 1967 2 Sheets-Sheet 2 4s 5 5 l 55\ /47 42 7' e2 INVENTOR. 82' 47 TATSUO KURATOMI 4 7 BY f/IJM United States Patent Ofiice 3,492,695 Patented Feb. 3, 1970 3,492,695 ULTRA HIGH PRESSURE-HIGH TEMPERATURE APPARATUS Tatsuo Kuratomi, 2-18 4-cl1orne, Hamatake, *Chigasaki-shi, Kanagawa-ken, Japan Filed June 14, 1967, Ser. No. 645,996 Claims priority, application Japan, July 16, 1966, 41/46,]t94 Int. Cl. B29c 3/00 US. Cl. 18-16.5 2 Claims ABSTRACT OF THE DISCLOSURE A pressure resisting die assembly for the production of synthetic diamonds by means of ultra high pressure and high temperature. An inner ring assembly is concentrically positioned in the die chamber between the reaction zone and the inner wall surface of the die so that force generated during pressing is imposed directly against the inner ring assembly rather than against the inner wall of the die.

DESCRIPTION OF INVENTION This invention relates to ultra high pressure-high temperature apparatus and more particularly to apparatus designed for the conversion of carbon to diamond by the application of ultra high pressure and high temperature.

The production of synthetic diamonds has been successfully carried out by applying high pressure and temperature to carbon and a solvent/catalyst to cause the transformation of the carbon into the diamond structure. The pressures normally required to carry out this transformation are on the order of 40,000 to 100,000 atmospheres. The temperatures required are on the order of 1600 C. Obviously, the apparatus for carrying out the carbon conversion must be specially designed to develop and contain the ultra high pressures required. A typical apparatus used in synthetic diamond processes is described in US. Patent 2,941,248 issued to Howard Tracey Hall. Apparatus of this type, however, is subject to relatively short die life due to cracks developing in the die walls. This deficiency is even more pronounced when such apparatus is scaled up for commercial production of synthetic diamonds. Replacing the dies is a relatively expensive and time-consuming operation.

Accordingly it is an object of this invention to provide an improved apparatus for producing ultra high pressures and high temperatures.

It is a further object of this invention to provide an ultra high pressure-high temperature apparatus having a substantially increased useful die life and which can be scaled up for efficient commercial production of synthetic diamonds.

These and other objects and advantages of this invention will be apparent from the specification and the appended claims when taken in connection with the drawings in which:

FIGURE 1 is a vertical sectional view of ultra high pressure-high temperature apparatus showing die wall failure.

FIGURE 2 is a horizontal sectional view of the apparatus of FIGURE 1 taken through line II.

FIGURE 3 is a vertical sectional view of ultra high pressure-high temperature apparatus made according to this invention.

FIGURE 4 is a vertical sectional view of another embodiment of a pressure resisting die assembly made according to this invention.

Referring to FIGURE 1, the apparatus shown is typical of that described in the aforementioned Hall patent. The apparatus comprises generally two opposed punch assemblies 11 and 11 and a pressure resisting die assembly, generally designated 12. The inner surfaces of punches 11 and 11' and die assembly 12 define a reaction chamber 13. Composite gasket assemblies 14 surround the reaction zone and act as a seal between punch assemblies 11 and 11 and die assembly 12.

Punch assembly 11 comprises a tapered portion 21 which gradually increases in diameter from tip 22 and which culminates in a substantially cylindrical base portion 23. It is believed that this description of punch assembly 11 will sufiice for punch assembly 11 which has the same configuration.

Referring to FIGURE 1 and FIGURE 2, die assembly 12 comprises a die 26 with a central aperture 16 therein provided with wall surface 27 which is tapered or converging-diverging with respect to the axis of die 26. Die 26 is reinforced with a pair of concentric binding rings, a portion of one binding ring 28 being shown, which are so fitted as to maintain die 26 under hoop compression. A safety ring (not shown) is provided around the periphery of the outermost binding ring.

In operation a suitable reaction vessel containing the material to be subjected to ultra high pressure is positioned in reaction chamber 13. Punch assemblies 11 and 11 are connected to suitable means for generating compressive force, such as a hydraulic press, and are driven toward each other thereby decreasing the volume of reaction zone 13 and compressing the sample contained therein. At the same time, by means not shown, high temperature is produced by electrical current within reaction chamber 13. The compressive forces generated by punch assemblies 11 and 11' are translated to the sample in reaction zone 13 which imposes lateral pressure on wall surface 27 of die 26 through gasket assembly 14.

The configuration of tapered portions 21 and 21' of punch assemblies 11 and 11', respectively, in combination with the converging-diverging configuration of wall surface 27 of die 26 resolve the lateral pressure on die 26 into a multi-directional force rather than the two-directional force encountered in conventional dies having substantially vertical 'wall surfaces. These forces are illustrated by arrows at 36, 37 and 38. The net effect is to resolve the purely lateral or horizontal force on wall surface 27 of die 26 into a multi-directional force and thereby cut down die failure due to tensile fracture. In addition, wall surface 27 of die 26 is maintained under compression to oifset axial tensile stress in die 26 due to the Poisson effect. As used herein the Poisson effect refers to the tensile stress in a body caused by the deformation of said body in the axial direction due to compression of the body in the lateral direction. The ratio of lateral deformation to axial deformation is known as Poissons ratio.

It has been found that. after several pressing cycles the forces imposed on wall surface 27 of die 26 begin to exceed the elastic limits of even such super-hard materials as cemented cabides from which die 26 is normally produced. When the elastic limit of the material of die 26 is exceeded, horizontal cracking occurs in accordance with the Poisson effect in the manner shown at 39, 39 in FIGURE 1. Cracking of die 26 is even more pronounced when the apparatus is scaled up to provide a larger reaction chamber for commercial production of synthetic diamonds. Once the die has been cracked the apparatus must be torn down and a new die substituted for the cracked die. This. results in lost production time and in creased manufacturing costs.

It has been found that the life of the die is substantially increased by providing, according to this invention, an inner ring assembly on the Wall surface of the die intermediate the reaction chamber and the die. It has also been found that the capacity of the reaction chamber can be 3 increased without increasing the probability of horizontal cracking of the die.

Referring to FIGURE 3, there is shown one embodiment of ultra high pressure apparatus made according to this invention. As in FIGURE 1, the apparatus generally comprises opposed punch assemblies 41 and 41 and a pressure resisting die assembly, generally designated 42.

Pressure resisting die assembly 42 comprises die 46 which is provided with a substantially central aperture 47 defined by inner wall surface 48 which is converging-di-,

verging with respect to the axis of die 46. Inner ring assembly, generally designated 51, is concentrically positioned with respect to die 46 in aperture 47 on inner wall surface 48. As shown in FIGURE 3 of the drawings, inner ring assembly 51 consists of upper and lower truncated cones 52 and 52', respectively, said cones being inverted with respect to each other so that the faces of smallest circumference of each of cones 52 and 52' are in abutting relationship when concentrically positioned in die 46. Inner surface 53 of assembly 51 is substantially parallel to the axis of die 46 and outer surface 54 is converging-diverging with respect to the axis of die 46 so that it is complementary to converging-diverging inner wall surface 48 of die 46 whereby inner ring assembly 51 is adapted for a flush fit on inner wall surface 48 of die 46. Die 46 is prestressed by binding rings 55 and 56 in the manner described in the Hall Patent 2,941,248.

Punch assemblies 41 and 41' are suitably mounted on pistons 61 and 61 of a suitable press, not shown. Punch assemblies 41 and 41 comprise tapered portions 71 and 71' which gradually increase in diameter from tips 72 and 72 and which culminate in base portions 73 and 73'. Punch assemblies 41 and 41' are coaxially mounted in opposition to each other and die assembly 42 is coaxially mounted between the punch assemblies. Reaction chamber 77 is defined by tips 72 and 72' of punch assemblies 41 and 41' and by inner surface 53 of inner ring assembly 51. Pressure is developed by moving one or both punch assemblies toward each other, thereby reducing the capacity of reaction chamber 77 and compressing material contained therein.

Gasket assembly 81 is provided in the manner shown in FIGURE 3 to seal reaction chamber 77 and to provide a stroke for punch assemblies 41 and 41' as well as to electrically and thermally insulate inner face 53 of inner ring assembly 51 and inner wall surface 54 of die 46. Gasket assembly 81 is provided with frusto-conical portions 82 and 82 which surround tapered portions 71 and 71 of punch assemblies 41 and 41' and a central, cylindrical portion 83 which serves as a liner for inner face 53 of inner ring assembly 51. Gasket assembly 81 is further provided with annular groove 84 of substantially the same dimensions as inner face 53 of ring assembly 51 for mounting said gasket assembly on inner ring assembly 51. Preferably, gasket assembly 81 is the composite sandwich type disclosed in the aforementioned Hall patent. The gasket material must be capable of undergoing large plastic shear distortions without losing shear strength. The shear strength of the material should be great enough to prevent gasket blowout during all parts of the operation cycle, i.e., during loading, holding, high temperature application, and unloading, yet not resist movement of the punch assemblies excessively. Among materials having these general properties are certain ceramics or stones, as for example pyrophyllite stone. Included also in the composite gasket assembly may be a mild steel gasket which acts as an electrical conductor.

The material of punch assemblies 41 and 41', die 46 and inner ring assembly 51 is preferably chosen from the highest strength metal or material available, since these components are subjected to high stress. Materials suitable for use in the apparatus of this invention include, but are not limited to the hardened die steels and cemented carbides. It is preferred to form the punch assemblies, die and inner cylinder 21sembly from cemented tungsten car- 4 bide such as Carboloy 44A supplied by the General Electric Company. This material comprises 94% tungsten carbide and 6% cobalt. Binding rings 55 and 56 may be produced from commercially available hardened alloy steels such as A151 4142 alloy steel.

The apparatus of this invention is used and operated in substantially the same manner as the apparatus shown in FIG. 1. The material to be subjected to ultra high pressure may be first placed in a suitable sample container for insertion in reaction chamber 77 or may be placed directly in said reaction chamber. One or both of punch assemblies 41 and 41 are driven into reaction chamber 77, thereby compressing the material contained therein. High temperature is generated by passing an electrical current between punch assemblies 41 and 41 through reaction chamber 77.

Pressure built up in reaction chamber 77 is directly imposed against inner surface 53 of ring assembly 51 through gasket assembly 81 and through ring assembly 51 to inner wall surface 48 of die 46 where it is resolved into a multi-directional force as described above in connection with the apparatus shown in FIGURE 1.

By acting directly on inner ring assembly 51 the force generated during pressing is only indirectly imposed on inner wall surface 48 of die 46 through assembly 51. As a result, the elastic limits of the die material are seldom exceeded and cracking of the die due to the Poisson effect is thereby greatly reduced.

Inner ring assembly 51 is directly subjected to high lateral compressive forces from reaction chamber 77, which forces may exceed the elastic limits of the material of ring assembly 51 and eventually cause horizontal cracking of the assembly according to the Poisson effect. This is offset to some extent by the vertical compressive force applied to inner ring assembly 51 by tapered portions 71 and 71 of punch assemblies 41 and 41' through gasket assembly 81. Moreover, in the preferred embodiment of this invention, inner ring assembly 51 is divided at its center into upper cone 52 and lower cone 52' which allows the ring assembly to compensate for deformation of the assembly material without horizontal cracking. In any event, it is recognized that after repeated use, portions of inner ring assembly will eventually crack. The individual cones or replacement assemblies can be easily installed and the cost of replacing the inner ring cones or the entire assembly is far less than the cost of replacing the die.

The effect of this invention is, therefore, to decrease the force acting on the die and to allow ultra high pressure to be generated in the reaction chamber. The elimination of direct force on the die and the reduction of indirect forces by the inner ring assembly of this invention substantially increases the useful life of the die. This invention also permits the enlargement of the reaction chamber without a corresponding decrease in die life.

It is within the scope of this invention that the inner face of the inner ring assembly be other than parallel to the axis of the die. For example, said inner surface may be inwardly converging-outwardly diverging with respect to the axis of the inner ring assembly in order to increase the life of the inner ring assembly. This embodiment is shown at FIGURE 4 wherein inner ring assembly 91 is concentrically positioned in aperture 47 of pressure resisting die 46 in the manner shown in FIGURE 3. Outer surface 94 of inner ring assembly 91 is complementary to and abuts against the converging-diverging inner wall surface of die 46. Inner surface 96 of inner ring assembly 91 is inwardly converging-outwardly diverging with respect to the axis of inner ring assembly 91.

It will be understood that the present invention is not limited to the specific materials and other specific details described above and may be carried out with various modifications without departing from the scope of the invention as defined in the appended claims.

I claim:

1. In a high pressure apparatus comprising (1) a pair of opposed punch assemblies, each of the punch assemblies having tapered terminal portions; (2) means for exerting pressure on the punch assemblies, whereby an object positioned between the tapered terminal portions can be subjected to high pressure; (3) a lateral pressure resisting member positioned between the opposed punch assemblies and provided with a substantially central aperture circumferentially surrounding the object to be subjected to high pressure, the member having a pressure resisting inner wall surface; and (4) a thermal and electrical insulating gasket positioned in the aperture of the lateral pressure resisting member and circumferentially surrounding the object and the tapered terminal portions of the punch assemblies, the invention which comprises a replaceable inner ring assembly comprising upper and lower members, the inner ring assembly being concentrically positioned in the aperture of the lateral pressure resisting member between the pressure resisting inner wall surface of the lateral pressure resisting member and the gasket, coaxial with respect to the punch assemblies, the upper and lower members having outer faces complementary to and abutting against the inner wall surface of the lateral pressure resisting member, and the lower end of the upper member abutting against the upper end of the lower member, whereby lateral force produced by pressing the object is first imposed against the inner ring and is reduced thereby.

2. The invention of claim 1, wherein the outer faces of the upper and lower members are truncated cones, and the upper cone is inverted with respect to the lower cone, so that the ends of smallest outside diameter of the cones are contiguous.

References Cited UNITED STATES PATENTS 2,941,247 6/ 1960 Bundy. 3,061,877 11/1962 Custers et al. 2,084,388 4/1963 Balhausen. 3,088,170 5/1963 Strong. 3,096,544 7/ 1963 Lundblad. 3,313,004 4/1967 Vahldiek et al.

WILLIAM J. STEPHENSON, Primary Examiner 

